12. Signal Transduction-Coupled Transcription Factors

Question 0

in order to activate or repress transcription, a transcription factor must be?

Answer 0

1. located in the nucleus

2. bind to DNA and/or interact with the basal transcriptional apparatus

Question 1

what do transcription factors do? (3 things)

Answer 1

1. affect DNA transcription through transactivation, DNA binding (or both)
2. have one or no DNA binding domains
3. can be constitutive (always on) or inducible (switched on)

Question 2

adaptive responses arise from

Answer 2

inducible TFs

Question 3

what are NLSs?

Answer 3

nuclear localization signals

sequences of basic amino acids found on proteins translated by soluble ribosomes of the cytoplasm & play a critical role in nuclear transport

Question 4

transport in and out of the nucleus occurs through?

Answer 4

nuclear pores

Question 5

oily spaghetti model

Answer 5

proteins rich with Nsp-1 repeats within the nuclear pore form a gel like matrix so that smaller molecules can freely diffuse through the gaps in the matrix & larger molecules are occluded & require transportation by the proper chaperones (GTP dependent)

Question 6

what do importins do?

Answer 6

recognize NLS and facilitate transport across the nucleus

Question 7

what is the monomeric G protein that regulates transport across the nuclear envelope?

Answer 7

Ran

Question 8

regulation of ran is similar to?

Answer 8

ras

Question 9

regulation of Ran:

Answer 9

GEF: stimulates GDP dissociation (activates)
GAP: stimulates hydrolysis of bound GTP by Ran’s inherent GTPase activity

Question 10

difference between ran & ras?

Answer 10

Ran is cytoplasmic, Ras is nuclear
GTP is abundant in the nucleus, GDP is abundant in the cytoplasm

^encourages active Ran within the nucleus & inactive Ran within the cytoplasm

Question 11

Ran’s role in transport?

Answer 11

nuclear protein binds its importin, transported into the nuclear environment

GTP-Ran can bind competitively for the importins NLS binding site

binding of GTP-ran to the importin stimulates its transport back through the nuclear pore and into the cytoplasm

Question 12

all nuclear bound proteins must have a ______

Answer 12

NLS

Question 13

what is the most important part of transcription regulation?

Answer 13

transactivation

Question 14

promiscuous binding

Answer 14

one TF can bind multiple DNA sequences specifically

i.e. GC receptor, binds 2 specific DNA sequences (one is an enhancer, one is a repressor)